The invention relates to a device for operating a parking lock of an automatic transmission in motor vehicles.
With the refinement of automatic transmissions in motor vehicles, transmission controls are already known, which also include the parking lock in the shift by wire system, such that it can no longer be operated mechanically, for example via a selector of the transmission control, with the possible exception of an emergency release. Understandably, such an automated control of the parking lock has to be secured such that in the case of errors in the control (for example electrical conductor interruption, short circuits, pressure loss in the hydraulic system) an unintended disengagement of the parking lock when the vehicle is stationary, or engagement of the parking lock during driving of the motor vehicle is excluded as far as possible.
Further, DE 196 25 019 A1 discloses, beside the hydraulic control of the operation of the parking lock, an electromagnetic locking element, which holds the pawl of the parking lock in the disengaged position for the hydraulic application, which in the case of a system failure in the hydraulic transmission control (for example by engine failure) prevents the parking lock from being unintentionally engaged. Further, a logical connection in an electronic transmission control device ensures, that the parking lock is automatically engaged or disengaged only in accordance with a selection device and/or defined operating parameters of the motor vehicle (for example ignition key position, vehicle speed, state of the parking brake, engine speed, etc.) by controlling corresponding control valves (not shown in DE) and locking elements. An advantageous locking element with low electricity consumption is disclosed, for example, in DE 198 34 156 A1.